Royal Institution. 225 



forms of the lines but the amount of power at the different distances ; 

 or not upon the mere amount, but on the circumstance that in every 

 case the body submitted to experiment has lines of different degrees 

 of force passing through different parts of it (for however different 

 the magnetic or diamagnetic conditions of a body and the fluid sur- 

 rounding it, they would not move at all in relation to each other in 

 a field of equal force) ; but whatever be the cause, it will be a con- 

 comitant of magnetic actions ; and therefore ought to be included in 

 the results of any law by which it is supposed that these actions are 

 governed. 



It has not yet been noticed that these general results appear to be 

 in direct opposition to those of Pliicker, who finds that diamagnetic 

 power increases more rapidly than magnetic power with increase of 

 force. But such a circumstance, if both conclusions be accordant 

 with facts, only shows that we have yet a great deal to learn about 

 the physical nature of this force ; and we must not shut our eyes to 

 the first feeble glimpses of these things, because they are inconsistent 

 on both sides with our assumed laws of action ; but rather seize 

 them, as hoping that they will give us the key to the truth of nature. 

 Bodies when subject to the power of the magnet appear to acquire 

 a new physical state, which varies with the distance or the power of 

 the magnet. Each body may have its own rate of increase and de- 

 crease ; and that may be such as to connect the extreme effect of 

 Pliicker, amongst paramagnetic bodies on the one hand, and the 

 extreme effects amongst diamagnetic bodies now described, on the 

 other ; and when we understand all this rightly, we may see the 

 apparent contradiction become harmony, though it may not conform 

 to the law of the inverse square of the distance as we now try to 

 apply it. 



Pliicker has already said, because of his observations regarding 

 paramagnetic and diamagnetic force, that no correct list of magnetic 

 substances can be given. The same consequence follows, though in 

 a different direction from what has now been stated, and hence the 

 reservation before made (p. 221). Still the former table is given as 

 an approximation, and it may be useful for a time. Before leaving 

 this first account of recent experimental researches, it may be as well 

 to state that they are felt to be imperfect and may perhaps even be 

 overturned ; but, that as such a result is not greatly anticipated, it 

 was thought well to present them to the Members of the Royal In- 

 stitution and the scientific world, if peradventure they might excite 

 criticism and experimental examination, and so aid in advancing the 

 cause of physical science. 



On a former occasion* the existence oi physical lines of force in 

 relation to magnetism and electricity was inferred from the dual 

 nature of these powers, and the necessity in all cases and at all times 

 of a relation and dependence between the polarities of the magnet, 

 or the positive and ne<;ative electrical surfaces. With respect to 

 gravity a more hesitating opinion was expressed, because of the dif- 



* Proceedings of the Royal Institution, p. 216. 



